Many protocols for use in communications exist in various configurations and layers. For example, hierarchical protocol model has been standardized as the seven-layer OSI reference model by the International Organization for Standardization (ISO), the International Telecommunication Union (ITU) and the like. Protocols can be classified according to this model. IP, presently the standard for the Internet, is a third layer (network layer) protocol; TCP and UDP are fourth layer (transport layer) protocols; HTTP, FTP, SMTP, POP and the like are fifth (session layer) or higher layer (session layer) protocols. Further, integrated protocols also exist including UPnP used in network devices and home electric products. It has become a common practice to mount these communication protocols on network devices and home electric products and thereby secure interoperability between each node.
As described above, however, various communication protocols exist, and standards, specifications and objects different from each other exist. Further, it is a fact that there are several kinds of different protocols to achieve the same object.
Therefore, upon purchasing a network device or a home electric product, a user must select a product having mounted thereon the same protocol. Further, even when a product having mounted thereon the same protocol is selected, it may be impossible to secure interoperability between these devices or between these products due to version-up of the protocol itself, appearance of a new protocol mounted on a new product, or the like.
To address such problem, Japanese Patent Laid-Open No. 8-97878 discloses a technique for performing communication between nodes on a network employing different protocols. In this document, there is disclosed a technique which associates information on which kind of protocol a node (device) on the network uses, with the address of the device and the kind of protocol, and stores the information, and based on the stored information, selects a protocol for each device and thereby performs communication. In order to implement this, several kinds of protocols must be preliminarily mounted on each device. In each device, there is a limitation on the number of mountable protocols, and thus it is practically impossible to mount all existing protocols. Further, with such technique, it is impossible to cope with protocols not mounted and unknown protocols.
As described above, in a case where network devices and home electric products using different protocols are used, or even in a case that the same protocol is used, interoperability cannot be secured between network devices and home electric products due to the difference of version.
Further, the technique described in the above document relates to a coping method employed typically before product shipment, and no method after product shipment is considered at all. To apply the technique described in the above document to products after shipment, a processing must be conducted such as allowing the user to update the firmware of the product or recalling the product to rewrite the program of the product, which is not practical.